Ampilfier with VCO-based ADC

Abstract

An amplifier includes an input circuit configured to receive an analog input signal and a feedback signal, and output an analog error signal based on the analog input signal and the feedback signal. An ADC is configured to convert the analog error signal into a digital signal in a phase domain. A digital control circuit is configured to generate a digital control signal based on the digital signal in the phase domain. An output circuit is configured to generate an amplified output signal based on the digital control signal, and a feedback circuit is configured generate the feedback signal based on the amplified output signal.

What is claimed is: 
     
       1. An amplifier, comprising:
 an input circuit configured to receive an analog input signal and a feedback signal, and output an analog error signal based on the analog input signal and the feedback signal; 
 an analog-to-digital converter (ADC) configured to convert the analog error signal into a digital signal in a phase domain; 
 a digital control circuit configured to generate a digital control signal based on the digital signal in the phase domain; 
 an output circuit configured to generate an amplified output signal based on the digital control signal; 
 a feedback circuit configured to generate the feedback signal based on the amplified output signal, and 
 wherein the ADC includes a voltage controlled oscillator (VCO) configured to output a frequency signal based on the analog error signal. 
 
     
     
       2. The amplifier of  claim 1 , wherein the digital control signal is a pulse width modulated (PWM) signal. 
     
     
       3. The amplifier of  claim 1 , wherein the ADC includes a Delta-Sigma ADC. 
     
     
       4. The amplifier of  claim 1 , wherein the ADC includes a phase quantizer configured to convert the frequency signal output by the VCO to a phase signal. 
     
     
       5. The amplifier of  claim 4 , wherein the phase quantizer is configured to compare the phase signal to a reference frequency. 
     
     
       6. The amplifier of  claim 5 , wherein the phase quantizer includes an exclusive OR (XOR) gate configured to receive the phase signal and the reference signal as inputs. 
     
     
       7. The amplifier of  claim 1 , wherein the digital control circuit includes a digital filter configured to receive the phase signal. 
     
     
       8. The amplifier of  claim 7 , wherein the digital filter includes a loop filter having an equivalent Laplace transfer function with at least one zero and one pole. 
     
     
       9. The amplifier of  claim 1 , wherein the feedback circuit includes a voltage divider. 
     
     
       10. The amplifier of  claim 9 , wherein the feedback circuit includes a filter. 
     
     
       11. The amplifier of  claim 3 , wherein the ADC includes a digital-to-analog converter (DAC) configured to convert the digital signal in the phase domain into an analog feedback signal received by the VCO. 
     
     
       12. The amplifier of  claim 1 , wherein the analog input signal is a differential input signal, and wherein the amplified output signal is a differential output signal. 
     
     
       13. The amplifier of  claim 1 , wherein the VCO is configured to receive the analog error signal directly from the input circuit. 
     
     
       14. The amplifier of  claim 1 , wherein the amplifier is a Class D amplifier. 
     
     
       15. A circuit, comprising:
 an input circuit configured to receive an analog input signal and a feedback signal, and output an analog error signal based on the analog input signal and the feedback signal; 
 an analog-to-digital converter (ADC) including a voltage controlled oscillator (VCO) configured to receive the analog error signal and output a frequency signal based on the analog error signal; 
 a quantizer configured to receive the frequency signal and compare the frequency signal to a reference signal to output a phase signal based on the frequency signal; and 
 a digital control circuit configured to receive the phase signal and output a pulse width modulated (PWM) signal based on the phase signal. 
 
     
     
       16. The circuit  claim 15 , further comprising an output driver configured to generate an output signal based on the PWM signal. 
     
     
       17. The circuit  claim 15 , wherein the ADC includes a Delta-Sigma ADC, and wherein the Delta-Sigma ADC includes a digital-to-analog converter (DAC) configured to convert the phase signal into an analog feedback signal. 
     
     
       18. The circuit  claim 15 , wherein the quantizer includes an exclusive OR (XOR) gate configured to receive the phase signal and the reference signal as inputs. 
     
     
       19. A method, comprising:
 receiving an analog input voltage signal; 
 comparing the analog input signal to a feedback signal to determine an analog error signal; 
 converting the analog error signal into a frequency signal with a voltage controlled oscillator (VCO) based on the analog error signal; 
 converting the frequency signal into a phase signal, including comparing the frequency signal to a reference signal; 
 converting the phase signal into a digital control signal based on the phase signal; and 
 generating an output signal based the digital control signal. 
 
     
     
       20. The method of  claim 19 , further comprising filtering the output signal to generate the feedback signal.